1. Field of the Invention
The present invention relates to a gas sensor having a gas sensor element for detecting the concentration of a particular gas, and to a manufacturing method therefor.
2. Description of the Related Art
A gas sensor is mounted to an intake system (e.g., an intake pipe or an intake manifold) of an internal combustion engine, such as a diesel engine or a gasoline engine, for controlling, for example, the condition of combustion by monitoring the concentration of a particular gas. Conventionally, such a gas sensor has the following structure: a gas detection element is held in a housing made of metal, and connection terminals, a separator, etc., provided at a proximal side (rear side) of the housing are protected with a tubular cover made of metal. The gas detection element has a cell in which a solid electrolyte and a pair of electrodes are provided. The gas detection element has electrode pads formed at its rear end for electrical communication with respective electrodes. The connection terminals are electrically connected to the respective electrode pads. An electromotive force is generated depending on a difference in concentration of a particular gas at the respective electrodes and output from the connection terminals.
However, the tubular cover made of metal involves a problem in that, since the structure is intricate, manufacture or assembly consumes time and labor. In order to cope with the problem, a structure described in Patent Document 1 has been developed in which a base member made of resin is connected to a proximal end portion of the housing. The base member of Patent Document 1 has a connector portion in which the connection terminals are disposed in an inserted manner. An external connector is inserted into the connector portion, thereby establishing an electrical connection to an external system.
Meanwhile, in order to mitigate impact imposed on a colliding object with which a vehicle having an internal combustion engine collides, a clearance must be provided between the hood and engine parts. In this connection, preferably, the length of outward projection of the gas sensor from the intake pipe is shortened.
[Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. H10-132779
3. Problems to be Solved by the Invention
Since a plurality of the above-mentioned connection terminals are provided in the connector portion, the connection terminals must be electrically insulated from one another. However, in the sensor described in Patent Document 1, when the connection terminals are to be attached afterward to the connector portion made of resin, the connection terminals must be press-fitted one by one into respective slits provided in the connector portion, resulting in reduced productivity. In the case where the connection terminals are insert-molded to the connector portion, a mold for the connector portion must have sufficient dimensional accuracy, and the structure of the mold becomes complicated, leading to increased cost.